Reproducing old machines with newer technology
rodsmallwood52 at btinternet.com
Tue Jul 14 13:42:47 CDT 2015
Back at a more general level. To my way of thinking what Bob Supnik did
in software can be extended by producing a hardware replica vehicle for
his code to give the illusion that the original system has been
recreated. A sort of machine Turing test if you will.
/On 14/07/2015 19:26, Chuck Guzis wrote://
> On 07/14/2015 10:55 AM, Noel Chiappa wrote:
>> I guess I don't know the 6600 that well (I have the book, and have
>> skimmed it
>> in the past). What are the novel features in the 6600 that were widely
>> adopted by other machines? (I listed the Atlas because of paging, and
>> the 801
>> because of RISC.)
> There are more than a few folks who call the CDC 6000 one of the first
> RISC machines. In particular, the 6600 with its instruction
> scheduling and reservation control, multiple functional units,
> instruction cache, etc. was quite noteworthy. You could easily
> recognize the earmarks of a very different machine of the time. The
> issues that arose when programming later RISC CPUs made me feel that I
> was back in familiar territory.
> 3-address architecture, 60 bit ones complement words, with separate
> sets of registers for addresses and indexing.
> A typical beginning programmer's problem was to write a CPU loop to
> move non-overlapping fields of words in the shortest amount of time
> (ECS not available). The best solution usually involved two words per
> iteration, with one instruction issue per cycle; bottom of the loop
> load (to overlap the branch) and top-of-the-loop store.
> Another challenge was to write a routine that could load and store the
> values of all registers from and to memory. Not as simple as it sounds.
> For me, one distinguishing feature is that there is no condition code
> register. You could branch on a register value being signed or zero,
> or compare and branch on the values of two index registers. Thus, the
> result of an operation was covered by the regular register reservation
> The I/O processors (PPUs) had access to all of CPU memory and
> essentially were their own world, using a 12-bit instruction set
> derived from the 160A. One could also say that the PPUs were only one
> machine with memory and registers being time-multiplexed to simulate
> 10 machines.
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